High Withstand Voltage Semiconductor Device Covered with Resin and Manufacturing Method Therefor
A high withstand voltage semiconductor chip mounted on a package or a board is covered with a sealing resin, and the resin is cured while a high voltage is applied between at least one of electrode terminals connected from a chip electrode or the chip via wiring of wires or the like and another electrode that necessitates a dielectric withstand voltage between the electrode and the electrode terminal during the curing. The sealing resin is provided by a synthetic high molecular compound structured in a manner that an organic silicon polymer C is constituted by alternately linearly linking an organic silicon polymer A having a crosslinking structure of siloxane with an organic silicon polymer B having a linear link structure of siloxane (Si—O—Si bond) by siloxane bond and the polymers are three-dimensionally linked together by covalent bond. With this arrangement, a dielectric withstand voltage capability, which is stable by suppression of an increase in the leakage current even when a high reverse voltage is applied and agrees with the designed value, can be obtained in a high withstand voltage semiconductor chip that is mounted on a board or a package and sealed with the resin.
The present invention relates to a semiconductor device whose withstand voltage is raised by covering a high withstand voltage semiconductor element with a resin.
BACKGROUND ARTA wide-gap semiconductor material made of silicon carbide (hereinafter referred to as SiC) or the like has excellent physical properties of a larger energy gap and a dielectric breakdown field intensity of about an order of magnitude greater than those of silicon (hereinafter referred to as Si) and attracts attention as a semiconductor material suitable for use in semiconductor devices of high heat resistance and high withstand voltage.
In the case of a conventional high withstand voltage semiconductor device employing SiC, a SiC semiconductor element having a high reverse breakdown voltage is housed in a metallic package. In order to improve the dielectric breakdown strength of space between electrodes of the SiC semiconductor element to which a high voltage is applied, the package is filled with an insulating gas such as sulfur hexafluoride gas.
The sulfur hexafluoride gas, which currently has a most excellent insulating property as an insulating gas, needs to be avoided from use from the viewpoint of preventing global warming since it contains fluorine, or a substance that destroys the ozone layer.
As a method for maintaining the excellent insulating property other than the filling of the sulfur hexafluoride gas, there is a method for covering the semiconductor element with a synthetic high molecular compound (generally called silicone rubber) that contains polymethyl phenyl siloxane having a linear structure of siloxane (Si—O—Si bond) or a synthetic high molecular compound that contains polyphenyl silsesquioxane having a crosslinking structure of siloxane. The synthetic high molecular compound is applied to cover the entire semiconductor element (semiconductor chip) in a liquid state of high viscosity and cured at a normal temperature or by heating to a temperature of about 100° C. to 200° C. As a result, a comparatively high insulating property can be maintained.
First patent document: JP 2002-356617 A
Second patent document: JP 2000-198930 A
In a semiconductor device of a rating of 5 kV having a cover obtained by applying a liquid high molecular compound of the silicone rubber or the like and curing the compound, or, for example, a diode, when a reverse voltage of 3 kV to 5 kV is applied between the anode electrode and the cathode electrode, a large leakage current of 2 μA to 8 μA flows between both electrodes as shown in
It is an object of the present invention to provide a high withstand voltage semiconductor device in which a semiconductor element that constitutes the semiconductor device is covered with a material having a high withstand voltage.
In order to achieve the above object, there is provided a high withstand voltage semiconductor device comprising:
a high withstand voltage semiconductor element having at least two electrodes between which a high withstand voltage is necessitated;
a first lead wire connected to one of at least the two electrodes;
a second lead wire connected to the other of at least the two electrodes; and
a resin coating material that is applied to cover the high withstand voltage semiconductor element, the electrodes and neighborhoods of connection portions of the first and second lead wires to the electrodes and is cured while a prescribed DC voltage is applied between the first and the second lead wires.
According to the present invention, an electric field is applied to the uncured resin by applying a DC voltage between at least two electrodes covered with the uncured resin. The inventor supposes that the molecules of the uncured resin are oriented in the direction of the electric field by the electric field, aligning the orientation direction, and the dielectric constant of the resin and the DC resistance are increased by curing the resin in a state in which the orientation direction is aligned. However, no theoretical analysis has been made at the present time. At any rate, the leakage current is reduced according to the actually measured results.
Also, there is provided a method for manufacturing a high withstand voltage semiconductor device including:
a high withstand voltage semiconductor element having at least two electrodes between which a high withstand voltage is required,
a first lead wire connected to one of at least the two electrodes, and
a second lead wire connected to the other of at least the two electrodes, wherein
the method comprises the steps of:
applying a resin to cover the high withstand voltage semiconductor element, the electrodes and neighborhoods of connection portions of the first and second lead wires to the electrodes; and
curing the resin while a prescribed DC voltage is applied between the first and second lead wires.
According to the present invention, the high molecular compound after being cured is softened by heating. By applying an electric field to the softened high molecular compound, the molecules of the high molecular compound are oriented in a definite direction. If the temperature is set back to the normal temperature in the above state, the orientation direction of the molecules is fixed in the definite direction. As a result, the resistance of the high molecular compound is maintained at a maximum value.
Also, there is provided a method for manufacturing a high withstand voltage semiconductor device including:
a high withstand voltage semiconductor element having at least two electrodes between which a high withstand voltage is necessitated,
a first lead wire connected to one of at least the two electrodes, and
a second lead wire connected to the other of at least the two electrodes, wherein
the method comprises the steps of:
applying a resin to cover the high withstand voltage semiconductor element, the electrodes and neighborhoods of connection portions of the first and second lead wires to the electrodes and curing the resin; and
heating the resin to a prescribed temperature while a prescribed DC voltage is applied between the first and second lead wires.
According to the present invention, by applying the resin to cover the semiconductor element and curing the resin while a prescribed reverse voltage is applied between at least two electrodes that necessitate a high withstand voltage of the semiconductor element, the reverse withstand voltage between at least the two electrodes can be raised. Moreover, after the resin has cured, by carrying out heating while the prescribed reverse voltage is applied between the two electrodes, an effect similar to the above can be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
1 board
2 SiC diode element
4 anode electrode
5 anode terminal
6 cathode electrode
7 cathode terminal
8 insulating material
9, 16, 18 resin
10 heating furnace
11 DC power source
12, 13, 14 SiC diode device
20 printed circuit board
21, 22 circuit conductor
DETAILED DESCRIPTION OF THE INVENTION High withstand voltage semiconductor devices and manufacturing methods therefor of preferred embodiments of the present invention will be described with reference to
The high withstand voltage semiconductor device and the manufacturing method therefor according to the first embodiment of the present invention are described with reference to
A thermosetting sealing resin 9 is applied to cover the SiC diode element 2, the lead wires 4a and 6a, the anode terminal 5 and the cathode terminal 7, which are constituted on the metal board 1 as described above and protruding from the upper surface of the metal board 1. The viscosity of the resin 9 is selected to an appropriate value so that the coating layer is mounded in a mountain-like shape as shown in
A general thermosetting resin can be used as the resin 9. Epoxy resin is an example of the thermosetting resin. More preferable resins include the following three resins.
1. A synthetic high molecular compound constituted of polydimethylsiloxane having a linear structure of siloxane (Si—C—Si bond) called Si rubber.
2. A synthetic high molecular compound constituted of polyphenyl silsesquioxane having a crosslinking structure of siloxane.
3. A synthetic high molecular compound structured in a manner that an organic silicon polymer C is constituted by alternately linearly linking an organic silicon polymer A having a crosslinking structure of siloxane with an organic silicon polymer B having a linear link structure of siloxane (Si—O—Si bond) by siloxane bond, and the organic silicon polymers C are three-dimensionally linked together by covalent bond generated by addition reaction.
The above synthetic high molecular compounds each have a good heat resistance and are able to be used by combining any one or a plurality of them.
The board 1 covered with the sealing resin 9 is put in a heating furnace 10 such as an electric furnace as shown in the schematic view of
A reverse voltage of 0 V to 5 kV was applied between the anode terminal 5 and the cathode terminal 7 of the thus-obtained SiC diode device 12 at the room temperature, and a leakage current between the anode terminal 5 and the cathode terminal 7 was measured. The result is shown in
A curve “d” in
The leakage current does not increase so much in the SiC diode device 12 of the present embodiment even when a high reverse voltage is applied. Therefore, a high withstand voltage characteristic can be maintained.
As is apparent from
In the SiC diode device of the present embodiment as shown in
In the example shown in
Although the examples each employing the SiC diode element 2 as a semiconductor element have been described in connection with the semiconductor devices of
Although the method for heating the resins 9, 15, 16 and 18 to a temperature of about 200° C. when the resins are cured has been described in the present embodiment, it is acceptable to perform the curing at a temperature of not higher than 200° C. or at the normal temperature depending on the kind of the resin.
The Second Embodiment A high withstand voltage semiconductor device and a manufacturing method therefor of the second embodiment of the present invention are described with reference to
If the present embodiment is described referring to, for example,
The present invention can be utilized for resin sealed type high withstand voltage semiconductor devices.
Claims
1. A high withstand voltage semiconductor device comprising:
- a high withstand voltage semiconductor element having at least two electrodes between which a high withstand voltage is necessitated;
- a first lead wire connected to one of at least the two electrodes;
- a second lead wire connected to the other of at least the two electrodes; and
- a resin coating material that is applied to cover the high withstand voltage semiconductor element, the electrodes and neighborhoods of connection portions of the first and second lead wires to the electrodes and is cured while a prescribed DC voltage is applied between the first and the second lead wires.
2. The high withstand voltage semiconductor device as claimed in claim 1, wherein
- the resin contains at least one selected from a group consisting of: a synthetic high molecular compound constituted of polydimethylsiloxane having a linear structure of siloxane (Si—O—Si bond) called Si rubber; a synthetic high molecular compound constituted of polyphenyl silsesquioxane having a crosslinking structure of siloxane; and a synthetic high molecular compound structured in a manner that an organic silicon polymer C is constituted by alternately linearly linking an organic silicon polymer A having a crosslinking structure of siloxane with an organic silicon polymer B having a linear link structure of siloxane (Si—O—Si bond) by siloxane bond, and the organic silicon polymers C are three-dimensionally linked together by covalent bond generated by addition reaction.
3. The high withstand voltage semiconductor device as claimed in claim 1, wherein the DC voltage is within a range of 100 V to 5 kV.
4. A method for manufacturing a high withstand voltage semiconductor device including:
- a high withstand voltage semiconductor element having at least two electrodes between which a high withstand voltage is required,
- a first lead wire connected to one of at least the two electrodes, and
- a second lead wire connected to the other of at least the two electrodes, wherein
- the method comprises the steps of:
- applying a resin to cover the high withstand voltage semiconductor element, the electrodes and neighborhoods of connection portions of the first and second lead wires to the electrodes; and
- curing the resin while a prescribed DC voltage is applied between the first and second lead wires.
5. A method for manufacturing a high withstand voltage semiconductor device including:
- a high withstand voltage semiconductor element having at least two electrodes between which a high withstand voltage is necessitated,
- a first lead wire connected to one of at least the two electrodes, and
- a second lead wire connected to the other of at least the two electrodes, wherein
- the method comprises the steps of:
- applying a resin to cover the high withstand voltage semiconductor element, the electrodes and neighborhoods of connection portions of the first and second lead wires to the electrodes and curing the resin; and
- heating the resin to a prescribed temperature while a prescribed DC voltage is applied between the first and second lead wires.
6. The high withstand voltage semiconductor device manufacturing method as claimed in claim 4, wherein
- the resin contains at least one selected from a group consisting of: a synthetic high molecular compound constituted of polydimethylsiloxane having a linear structure of siloxane (Si—O—Si bond) called Si rubber; a synthetic high molecular compound constituted of polyphenyl silsesquioxane having a crosslinking structure of siloxane; and a synthetic high molecular compound structured in a manner that an organic silicon polymer C is constituted by alternately linearly linking an organic silicon polymer A having a crosslinking structure of siloxane with an organic silicon polymer B having a linear link structure of siloxane (Si—O—Si bond) by siloxane bond, and the organic silicon polymers C are three-dimensionally linked together by covalent bond generated by addition reaction.
7. The high withstand voltage semiconductor device manufacturing method as claimed in claim 4, wherein the DC voltage is within a range of 100 V to 5 kV.
8. The high withstand voltage semiconductor device manufacturing method as claimed in claim 5, wherein a temperature of the heating is 30° C. to 300° C.
7. The high withstand voltage semiconductor device manufacturing method as claimed in claim 5, wherein
- the resin contains at least one selected from a group consisting of: a synthetic high molecular compound constituted of polydimethylsiloxane having a linear structure of siloxane (Si—O—Si bond) called Si rubber; a synthetic high molecular compound constituted of polyphenyl silsesquioxane having a crosslinking structure of siloxane; and a synthetic high molecular compound structured in a manner that an organic silicon polymer C is constituted by alternately linearly linking an organic silicon polymer A having a crosslinking structure of siloxane with an organic silicon polymer B having a linear link structure of siloxane (Si—O—Si bond) by siloxane bond, and the organic silicon polymers C are three-dimensionally linked together by covalent bond generated by addition reaction.
Type: Application
Filed: Oct 5, 2005
Publication Date: Nov 15, 2007
Inventors: Shinichi Okada (Osaka-shi), Yoshitaka Sugawara (Osaka-shi), Katsunori Asano (Osaka-shi), Daisuke Takayama (Osaka-shi), Yoshikazu Shoji (Arakawa-ku), Tadashi Janado (Arakawa-ku), Takashi Sueyoshi (Arakawa-ku), Ken-Ichiro Hiwatari (Arakawa-ku)
Application Number: 11/664,586
International Classification: H01L 23/29 (20060101); H01L 21/56 (20060101);